Ron Paul, the libertarian who ran for president three times, said Tuesday he could possibly support Donald Trump "if he argued for the free market."
"But this is jokingly," Paul told CNBC's "Squawk Box." "Most people have rolled over and said, 'Yeah, we complained two months ago about tariffs, but he probably wasn't serious about it.' We don't know what he's serious about. Now, I think a tariff war would be horrible right now."
Trump, the presumptive GOP nominee, has said he would place a 45 percent tariff on Chinese goods in his attempts at making "America great again."
Paul also said although it is important to keep U.S. borders protected, Trump's proposals are foolish.
"This idea of building the China Wall on our southern border and making Mexico pay for it, I don't understand how people say 'that's a good idea,' and that's his rallying cry. I find that a little bit silly," the former Texas congressman said.
Paul said Trump recently made a good point about undocumented immigrants coming in and being treated better than some U.S. veterans.
According to a September report from the Center For Immigration Studies, 62 percent of households headed by undocumented immigrants used one or more welfare program in 2012.
Paul was the Libertarian Party candidate for president in 1988 and ran as a Republican in 2008 and 2012. He is the father of Sen. Rand Paul, who unsuccessfully ran against Trump for the GOP nomination.
Correction: This story was revised to correct that Ron Paul ran for president as a Libertarian in 1988 and as a Republican in 2008 and 2012.